Following concerns that there might be a problem with the iPhone 5's camera thanks to reports of a purple-colored lens flare appearing in photos, Apple posted a knowledge base article
acknowledging the effect and also saying it's normal for digital cameras.
iPhone 5's purple haze, or at lest our artist rendition
Apple described the effect as, "A purplish or other colored flare, haze, or spot is imaged from out-of-scene bright light sources during still image or video capture."
The knowledge base article goes on to state,
Most small cameras, including those in every generation of iPhone, may exhibit some form of flare at the edge of the frame when capturing an image with out-of-scene light sources. This can happen when a light source is positioned at an angle (usually just outside the field of view) so that it causes a reflection off the surfaces inside the camera module and onto the camera sensor. Moving the camera slightly to change the position at which the bright light is entering the lens, or shielding the lens with your hand, should minimize or eliminate the effect.
In other words, Apple is saying the problem isn't with the iPhone's camera but instead with users pointing it at bright light sources. While that response won't please some iPhone owners, it is accurate because bright lights can cause lens flares in images -- just ask JJ Abrams